gh-100344: Provide C implementation for asyncio.current_task

[itamaro]

Implementing it in C makes it about 4x-6x faster

Microbenchmark:

# bench.py

import time
import timeit
import asyncio

ITERS: int = 10**6
NANO: int = 10**9
NANO_PER_ITER: float = NANO / ITERS

async def main():
   # avoid load attr noise
   py_current_task = asyncio.tasks._py_current_task
   c_current_task = asyncio.tasks._c_current_task

   asyncio.current_task() # warmup
   py_current_task() # warmup
   c_current_task() # warmup

   print(
      "current_task: {}ns".format(timeit.timeit(py_current_task, number=ITERS, timer=time.process_time) * NANO_PER_ITER)
   )
   print(
      "current_task: {}ns".format(timeit.timeit(c_current_task, number=ITERS, timer=time.process_time) * NANO_PER_ITER)
   )

asyncio.run(main())

a few runs on MacBook Pro
2.4 GHz 8-Core Intel Core i9
64 GB 2667 MHz DDR4:

debug build:

~/work/pyexe/main-dbg ⌚ 9:57:34
$ ./python.exe bench.py
[py] current_task: 606.234ns
[c] current_task: 104.47699999999993ns

~/work/pyexe/main-dbg ⌚ 9:57:59
$ ./python.exe bench.py
[py] current_task: 631.856ns
[c] current_task: 110.22500000000002ns

~/work/pyexe/main-dbg ⌚ 9:58:08
$ ./python.exe bench.py
[py] current_task: 637.746ns
[c] current_task: 105.03899999999999ns

~/work/pyexe/main-dbg ⌚ 9:58:16
$ ./python.exe bench.py
[py] current_task: 621.3169999999999ns
[c] current_task: 103.01300000000002ns

opt build:

~/work/pyexe/main-opt ⌚ 10:33:17
$ ./python.exe bench.py
[py] current_task: 128.743ns
[c] current_task: 31.997999999999998ns

~/work/pyexe/main-opt ⌚ 10:33:24
$ ./python.exe bench.py
[py] current_task: 126.388ns
[c] current_task: 32.64599999999998ns

~/work/pyexe/main-opt ⌚ 10:33:26
$ ./python.exe bench.py
[py] current_task: 137.053ns
[c] current_task: 32.066999999999986ns

~/work/pyexe/main-opt ⌚ 10:33:28
$ ./python.exe bench.py
[py] current_task: 131.17800000000003ns
[c] current_task: 32.06600000000001ns

Co-authored-by: @pranavtbhat

• Issue: Provide C implementation for asyncio.current_task #100344

[bedevere-bot]

🤖 New build scheduled with the buildbot fleet by @pablogsal for commit 76cbbc6 🤖

If you want to schedule another build, you need to add the :hammer: test-with-refleak-buildbots label again.

[pablogsal]

Congrats @itamaro! Your PR has been selected to try the new refleak buildbot label! 😉

[itamaro]

Your PR has been selected to try the new refleak buildbot label! 😉

Such an honor, thank you @pablogsal 😛

Checking out a few of the additional refleak test runs, I saw (across different buildbots): timeout, failure of test_nntplib, and failure of test_logging.
While none of these indicates new refleaks nor seems obviously related to this PR, it did nudge me to take a closer look, and I did find refleaks using:

./python.exe -m test test_asyncio.test_tasks -v -m "*current_task*" -R 3:3
...
OK
.
test_asyncio.test_tasks leaked [2990, 2988, 2990] references, sum=8968
test_asyncio.test_tasks leaked [896, 894, 894] memory blocks, sum=2684
test_asyncio.test_tasks failed (reference leak)

== Tests result: FAILURE ==

1 test failed:
    test_asyncio.test_tasks

Total duration: 23.6 sec
Tests result: FAILURE

I think the issue is not decrefing the loop when getting it from _asyncio_get_running_loop_impl. I'm pushing a fix that made it pass for me locally - let's see what the buildbots think 🤞

[gvanrossum]

I'm waiting for the benchmark test suggested by Mark in the issue.

[itamaro]

I'm waiting for the benchmark test suggested by Mark in the issue.

replied on the issue and pushed the python optimization @markshannon suggested for ~40% speedup.
my suggestion is to do both optimizations 😄

[kumaraditya303]

The tests need to be adjusted to test both pure python and c implementation. Also looks like there are merge conflicts.

[bedevere-bot]

A Python core developer has requested some changes be made to your pull request before we can consider merging it. If you could please address their requests along with any other requests in other reviews from core developers that would be appreciated.

Once you have made the requested changes, please leave a comment on this pull request containing the phrase I have made the requested changes; please review again. I will then notify any core developers who have left a review that you're ready for them to take another look at this pull request.

[itamaro]

I have made the requested changes; please review again

[bedevere-bot]

Thanks for making the requested changes!

@kumaraditya303: please review the changes made to this pull request.

[kumaraditya303]

LGTM, I'll wait for @gvanrossum's review before merging.

[gvanrossum]

@kumaraditya303 If you agree go ahead and merge.

[itamaro]

Is it still ok to push another change to revert the Python implementation as discussed on the issue, after approval?

[kumaraditya303]

Is it still ok to push another change to revert the Python implementation as discussed on the issue, after approval?

That's fine, I'll review anyways before merging so go ahead!

[kumaraditya303]

LGTM

[kumaraditya303]

Merged, thanks for working on this!